INSIDE THE TWO YEARS THAT SHOOK FACEBOOK—AND THE WORLD

ONE DAY IN late February of 2016, Mark Zuckerberg sent a memo to all of Facebook’s employees to address some troubling behavior in the ranks. His message pertained to some walls at the company’s Menlo Park headquarters where staffers are encouraged to scribble notes and signatures. On at least a couple of occasions, someone had crossed out the words “Black Lives Matter” and replaced them with “All Lives Matter.” Zuckerberg wanted whoever was responsible to cut it out.

“ ‘Black Lives Matter’ doesn’t mean other lives don’t,” he wrote. “We’ve never had rules around what people can write on our walls,” the memo went on. But “crossing out something means silencing speech, or that one person’s speech is more important than another’s.” The defacement, he said, was being investigated.